Horizontal axis wind turbines have rotors with horizontal rotor shafts located at the top of a tower. The rotor shaft must be pointed in the wind in order to extract wind energy. To keep power generation by a horizontal axis wind turbine in an optimum range the rotor is typically rotated about a vertical axis in case of a change of the wind direction so as to follow the wind direction. The angle by which the rotor is rotated during this process is called yawing angle or azimuth angle. The rotation is performed by a yawing system that typically comprises a ring gear, a number of pinion gears meshing with the ring gear and controller for controlling the yaw angle. Such yawing systems are, for example, disclosed in EP 2 189 656 A2, US 2003/0160456 A1 or US 2009/0232652 A1.